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Abstract

The relationship between the surface segregation, boron poisoning and surface exchange coefficients of La0.6Sr0.4Co0.2Fe0.8O3−δ, (LSCF) cathodes of solid oxide fuel cells (SOFCs) is studied on dense bar samples using SEM, SIMS and conductivity relaxation method. The SEM results clearly indicate that the segregation on the LSCF surface occurs after heat-treatment at 700–800°C for 48 h, forming isolated particles on the LSCF surface. The presence of volatile boron species accelerates grain growth of the segregated particles and reacts with LSCF. The depth of boron reaction layer after heat-treatment in the presence of E-glass at 700°C, 750°C and 800°C for 48 h was 2, 5 and 40 nm, respectively. The depth profiles analysis of SIMS indicates that there is segregation and enrichment of constituent elements of LSCF on the electrode surface, in line with the depth profile of boron species on the LSCF sample surface layer. Boron deposition and poisoning deteriorates the surface exchange and diffusion processes for the oxygen reduction reaction on LSCF. After exposed to boron at 800°C for 48 h, the surface exchange coefficient, Kchem is 6.0 × 10−5 cm s−1, more than one magnitude lower than 1.1 × 10−3 cm s−1 of as-prepared LSCF samples.

Chromium deposition and poisoning is one of the most fundamental issues affecting the performance stability of La0.6Sr0.4Co0.2Fe0.8O3-d (LSCF) perovskite electrode materials used in intermediate temperature solid oxide ...

Effect of volatile boron species on the properties of La 0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode materials has been studied in detail by using porous electrode coatings and dense bar samples. Prior to the characterization, ...

In this study, the effect of the temperature on the surface segregation and Cr deposition on La0.6Sr0.4Co0.2Fe0.8O3-ä(LSCF) cathodes is investigated using confocal laser Raman spectroscopy and electrical conductivity ...